fourthirdsinfo

Tuesday, 4 January 2011

Lightroom 3 can perform automatic adjustment of lens imperfection, including CA, lens shading and geometric aberrations. Although SHG lenses are excellent in all three aspects, they do show signs of each and therefore correction can be beneficial. Adobe does not supply Olympus profiles, but provides us with a tool that can be used to create them. This is just what I did - you can find the writeup, sample pictures (before/after) and the profiles themselves on my related technical page. I even include a comparison with the Nikkor 24-70 (yes, the new one)!

I have created profiles for the 14-35, the 35-100 and the 50 macro for various apertures shooting RAW. My experience is that the most needed correction is fixing geometric distortion of the 14-35 at larget fields of view. The 14-35 around 35, the 35-100 and the 50 has little to no distortion. Lens shading is also nicely treated, and is most visible with the 14-35, less with the 35-100 (but the result is strange - see the text) and is negligible with the 50 macro. All in all, this is a package worth considering if you are into this combination of stuff.

Wednesday, 28 April 2010

If you are a regular reader of our blog, you could notice that the avaliability of true multi-aspect ratio is a sensitive part of my heart. I have written about it many times. To better illustrate the operation of this method, I have made some new animations based on flash.

conventional method of almost every camera:cropping the image and droping out the pixels(move the cursor over the animation to rotate it)

Thursday, 15 April 2010

I have planned for a long time to write a post about video mode of dSLRs. The announcement of Panasonic micro4/3 type professional videocamera have given me a new impulse to do this. Let's start with a quote from me: "Probably all Micro FourThirds camera will be able to record movie but maybe a videocamera-system with interchangeable lenses is among the main goals of Panasonic. August 5. 2008." Of course, I smirked a lot when I read about AG-AF100 some days ago.

A first thought of many might be that this will be the ultimate video system. But we have to clearly define the category of this equipment to judge its applicability. There are two main categories in the professional videography market which we have to talk about: cameras equipped with three relatively small (1/3'' or 2/3'' type) sensors, and large, single sensor cameras (35mm Arri stantard type, close to APS-C size in photograpy).

trichroic beam splitter of a 3CCD videocamera
(move the cursor over the animation to rotate the prism)

Single sensors use a filter array over the pixels to determine the color of the light. Color filter passes only a small part of incoming light by dropping out the remaining part of it. The other method to sense the color is to split the light beam into its color components by a trichroic prism. It is a complex and precise optical system which uses three monochromatic sensors. This solution is expensive, requires lots of space and requires special optical design of the attached lens but is two to three times more efficient than single sensors with color filter arrays.

The introduction of 3CCD cameras was a milestone in the video world. Every low-light situation where the videographer has not chance to use a lot of artifical light, the three sensor setup is very useful. You might think that a large sensor is a substitute for it, but it is in fact not. The shallow depth of field of a large sensor is not acceptable in many cases and stopping down to achieve the required sharpness, you lose light and thus the advantage of the large sensor. The 1/3'' type sensors allow engineers to create lense systems with high zoom ratio (>10x) and fast aperture (>f/2). It is impossible to design comparable lenses for 4/3'' sensors. To sum up, the advantages of a large, single sensor (variable depth of field and good signal to noise ratio) can be exploited only if the situaton is allows it and these advantages are partially substitutable by fast lenses of multi-sensor cameras. On the other hand, the gain in light-efficiency with three sensors is an absolute profit. Unfortunately, the flange distance of micro 4/3 standard is not small enough to place three sensors into the camera.

So in what area are videocameras with large sensor usable? Movies, videoclips, in studio and most outdoor situations, the advantages can outweigh the disadvantages. But to record the most important indoor video-report of my life I would take a 3CMOS camera with me. The whole question will of course be moot if one of the manufacturers develops a multi-layer sensor with the same efficiency as the three sensor method. But there are only plans and patents about this idea, and the single presently available technology, Foveon, is in a lightyear away from this quality.

Video mode of dSLRs is often criticized for a typical flaw. In videocameras equipped with CCD the interline type is used instead of fullframe transfer type. Exposure and reading of the image is totally separated in interline CCDs. The photosites can not transmit the charge to nearby photosite, but there are CCD registers between every coloumn which are covered from light. At the end of the exposure, after the charge of photosites has been loaded into the masked CCD coloumns, a new exposure starts while the previous frame is being read. Thanks to this solution the exposure starts at same time on the whole surface of the sensor.

Interline CCD vs. CMOS

CMOS sensors are able to produce moving picture in itself because their pixels are individually addressable and readable. But a pixel can do only one thing at a time, so the reading electronics has to continously scan the sensor and start the exposure at the row last read. This results to an odd phenomenon called "rolling shutter effect". The name deriving from distortion produced by focal plane shutters at high shutter speed and on moving theme. Horizontally moving (relatively to optical axis) objects will be tilted, vertically moving objects will be compressed or lengthened.

As the amplifiers and switches in CMOS sensors, the masked coloumns in interline CCDs also reduces the efficient surface of pixels. The microlenses help to collect more light in both type of these devices. The rolling shutter effect is not accepptable in lots of applications, however manufacturing of cameras equipped with CMOS is cheeper and these sensors produce less noise due to high level of integration (on chip A/D, noise reduction etc.). By increasing frame rates and digitally combining these frames helps to make virtually invisible the imperfection of CMOS sensors. Panasonic will use this solution in AG-AF100 too.

Another important question is the lens strategy of Panasonic. The only lens which comparable for professional videocameras from point of view of AF drive is the 14-140 HD due to its linear motor, but its maximum aperture makes it a toy, rather than a professional equipment. I do not think that Panasonic wants to focus only professional segment because the micro 4/3 bayonet compatibility would be pointless, but it is a telling sign that the mockup was presented with a Zuiko Digital 14-35mm 1:2 mounted on it. Yes, the professional market will not accept lenses with f/5.6 maximum aperture, Panasonic has to clearly communicate that there will be more price and performance lens category to create the possibility of a smooth transition for advanced users. Maybe, photograpers will profit from this too thanks to new, fast and high quality prime lenses.

A welcome news in the announcement that AG-AF100 will support 1080p mode, and 50 or 60 frame per second at smaller resolution. I hope, we will meet this feature in Olympus cameras, because all of new Canon video-dSLRs can do it. I think the most positive impact of Panasonic's new system that it speeds up the development of the 4/3 size sensors, and this is what we have been waiting for since 2003.

Wednesday, 24 March 2010

There is a lot of news floating around the web these days regarding Olympus's first really affordable non-SLR system camera, the E-PL1. For various reasons, we are excited to finally have this camera at our disposal. It is not only its 12 megapixel sensor and the possibility to re-test the Top Pro lenses that makes this unit interesting, but also checking out the new imager-based AF and its video recording capabilities. We shall come back to these topics in the near future. So far, the collapsible 14-42mm lens looks fine to us, but as usual, we shall be putting emphasis on the Top Pro gear. As a first shot at the matter, please consider the monster the E-PL1 and the 14-35mm f2.0 forms together (using the MMF-2 adapter, bundled to the E-PL1 DZK)....

Thursday, 21 January 2010

Hi there,I guess many of you dream of owning the 14-35mm f2.0 as much as I did before having the strange chance to get it in a peculiar way. Well, it is a nice beast, but there can be a lot of headache with it. And I am not referring to the outrageous AF performance I am planning to write about - well, for a year now. No, it is not AF. It is the front lens.You know what this is?Well, this is the front lens of my copy and a dent on it! OMG - a dent! This is how it looks like as a 100% crop from the original:Ugly, isn't it?

It is, but this is why I got the discount that allowed me to buy the copy. Knowing that even a big dent like this on the front lens does not affect image quality substantially (causing perhaps some weak flare or a tiny loss of contrast - ironically, reducing two important characteristics of this lens - never mind), I was very happy with the purchase and thougth that the previous owner was a careless bastard (OK, I do like the guy). But I was too happy too soon.

After some time, two smaller dents appeared after my own use. I could not believe what has happened. The first dent was caused by the lens cap falling off and something hard knocking to the lens, that is for sure. But what about the last two? I could not recall anything like this happening. And then I knew: it was the lens cap.

Although not as clever as the mechanism on the Nikon and Canon 24-70mm f2.8 zooms, Olympus supplies a shade as standard for this lens. It is a fine peace (covered with velvet in the inside), but it does not allow one to easily put on the lens cap. Even though the cap has a "pinch-type" release that can be operated even with the shade on, it is difficult to put on when the shade is on the lens. After the second and the third scratch I have realised: the original owner was not more careless than anyone else - this design is what provokes hesitant putting on the cap and thus the rim of the cap reaches not the rim of the front part of the lens barrel, but the front lens itself. The result is inevitably a scratch or a dent after some use.I was never a friend of lens filters, because of the possible adverse effect on image quality. Since that moment of illumincation however, I prefer having cap on the lens. One good choice is the Clear B+W SX-PRO - this is a slim model that allows you to use the original lens cap (if you want to, after this).

Just to repeat: if you own a 14-35mm f2.0, you should seriously consider putting on a good quality clear or UV filter for protection. Yes, it will probably decrease the image quality a tiny bit, but will save some serious money for you.

Yours,Zs

PS: I was actually planning to buy the B+W filter ever since I was shooting with the 14-54mm in rain. Water resistance is nice, but if the water creates a film on your front lens, you can only save the lens, but not using it. The B+W filter has no windscreen-wiper either, but collects water, repells it if possible, but always makes removing it easier. Right, just one more reason.

Monday, 21 December 2009

Thanks to our "other" tasks, we shall not develop this blog/site to what we wanted when we started. Because of this, we do not renew the domain subscription and therefore it will be free as of 29. January 2010. Stay tuned for the opportunity if you are interested! We hope that You can provide better service to the four-thirds community than we could.

We also hope that we can spare some time for actual photography in the time freed up. Nevertheless, as we continue ot use four-thirds cameras in the future, this blog stays up and will hopefully receive new post too.

Wednesday, 25 November 2009

Ever wondered why the information flow has stopped on this site? Well, there are many reasons, connected to "other", and to be honest: more binding obligations. But because we still think that four-thirds is a sane option to choose, we are planning to continue our efforts. Due to our access to various new lenses, we are planning to re-shoot the popular "Big gun Test". The long due reviews of the 14-35, the 35-100 will be done and published. And besides the information bits, we are planning to do some system comparisons (say, a Canon 1D + 70-200f4 IS vs. E-3 + 35-100mm f2).

Until then, please enjoy an example of sharpness at 100mm f2 below (which actually surprised us as we have not experienced such sharpness at 100mm on the E-1 when we have done the review):

[click for full sized jpg available from the photo's page - "All sizes" menu option]